Vitamin E-doped cross-linked polyethylene (VEPE) has encouraged the use of larger heads in thinner liners in total hip arthroplasty (THA). However, there are concerns about wear and mechanical failure of the thin liner, especially when metal heads are used. The aim of this randomized controlled trial was to investigate if the use of a large metal head in a thin VEPE liner would increase polyethylene wear compared with a standard 32-mm metal head and to compare periacetabular radiolucencies and patient-reported outcomes in THA.

96 candidates for uncemented THA were randomly allocated to either the largest possible metal head (36–44 mm) that could be fitted in the thinnest available VEPE liner (intervention group) or a standard 32-mm metal head (control group). The primary outcome was proximal head penetration (PHP) measured with model-based radiostereometric analysis (RSA). Secondary outcomes were periacetabular radiolucencies and patient-reported outcomes. The mid-term results of the trial at 5 years are presented.

Median total PHP (interquartile range) was -0.04 mm (−0.12 to 0.02) in the intervention group and -0.03 mm (=0.14 to 0.05) in the control group (p=0.691). The rates of periacetabular radiolucencies were 1/44 and 4/42 (p=0.197), respectively. Patient-reported hip function and health-related quality of life did not differ between the groups, but participants in the intervention group reported a higher level of activity (median UCLA rank 7 vs 6, p=0.020). There were 5 revisions caused by dislocations (2), periprosthetic fracture (1), stem subsidence (1), or iliopsoas impingement (1).

Large metal heads in thin VEPE liners did not increase liner wear and were not associated with liner failure 5 years after THA.

Aims

We aimed to investigate if the use of the largest possible cobalt-chromium head articulating with polyethylene acetabular inserts would increase the in vivo wear rate in total hip arthroplasty.